1. Technical Field
The present invention relates to printers, and, in particular, relates to methods for detecting printing material amounts in printing material containers attached to printers.
2. Related Art
Ink containers attached to ink-spray printers are provided with sensors for detecting the amount of remaining ink, such as piezoelectric elements having the characteristics of expanding and contracting when a voltage is applied. Because piezoelectric elements generate a residual vibration after a voltage has been applied and then output an output signal by this residual vibration, when the amount of ink is detected using a sensor provided with a piezoelectric element, the printer is able to determine whether there is ink remaining in an ink container by applying a voltage to the piezoelectric element and measuring the frequency of the output a signal that is outputted from the sensor. Specifically, the printer is able to determine whether t the ink remaining in the ink container is more than a specific amount by measuring the vibration frequency of the sensor included in the output signal.
The measurement accuracy of the vibration frequency is able to be improved by increasing the amplitude of the vibration of the sensor by having the frequency of the voltage that is applied to the piezoelectric element be the natural frequency of the sensor.
However, the natural frequency of the sensor may change depending on a variety of factors. For example, there are changes caused by the ink that is adhered to the sensor when the ink stored in the ink container remains in the ink container at less than a specific amount, and changes caused by damage to the sensor part in the ink container. When the natural frequency changes, the accuracy of the measured vibration frequency drops because it is not possible to obtain an adequate amplitude in the vibration of the sensor. As a result, the accuracy of the measurement of the ink volume reduces.